The present invention relates generally to fluid spray guns and more particularly to compact multi-fluid component spray guns for use in low pressure, airless nozzle fiberglass spraying systems with external resin catalyst mixing.
Fiberglass spraying devices, and particularly hand held units, have previously employed a number of different spraying methods in attempts to provide well-mixed, properly shaped fluid spray flows in the most efficient manner possible. Typical fiberglass spraying apparatus supply fluid resin and fluid catalyst to a nozzle for internal or external mixing. With internal mixing, catalyst fluid may typically first be atomized by mixing with air and then directed into the path of the fluid resin at the nozzle interior. After resin-catalyst mixing, the resulting fluid is forced through a common nozzle and directed at the work piece. Internal mixing requires time consuming and expensive cleaning of the nozzle and mix chambers after each use.
With external mixing, both catalyst and resin fluids may typically be forced through separate spray nozzles prior to mixing. These nozzles are directed such that the catalyst and resin spray flows intersect to permit mixing prior to contact with the work piece. If the resin is not atomized prior to spraying, the process is often called "airless." Such external mixed sprayers may not need extensive cleaning after each use, but typically require high fluid pressures. Reinforcing fibers may typically be directed into the mixed spray path of either internal or external mix sprayers to be wetted thereby and carried to the work piece.
Major concerns in designing and operating fiberglass sprayers include providing a thoroughly mixed spray, to assure proper curing and work piece uniformity, as well as larger transfer efficiencies and lower operating costs. The term "transfer efficiencies" refers to the amount of material applied and adhering to the work product compared with the amount of waste material left in the atmosphere or elsewhere, such as the floor of the production room. Since fiberglass resin and catalyst materials are expensive and catalyst and spray mixture fumes present serious health hazards for production personnel, it is desirable to achieve as high a transfer efficiency as possible. Operating costs may be reduced by, for example, decreasing the amount of down time for system maintenance, repair, or cleaning and lowering the pumping pressure capacity needed. Further, if the spray flow fan is properly configured, production time itself may be reduced.
In prior fiberglass sprayers, a trigger mechanism operates a single piston which typically controls the flow of resin and catalyst to a mixing chamber. The piston works with either external or internal mixing chambers. In order to open both the resin and catalyst valves, a large piston is required to obtain sufficient forces for the opening. The valves are connected to this piston by connecting rods. If the connecting rod becomes kinked, the valve has a tendency to stick or stay open. When the trigger is released, spring mechanisms force the valves to a closed position. If the valve becomes sticky, the springs have a tendency not to completely close the valve mechanism and leaking of resin and/or catalyst is possible.
Also these single piston guns require a large piston, making the guns very heavy to handle. Upon operation over a long period of time, the operator can become fatigued and not apply the spray flow to the work piece properly.
After using these prior spray guns for a long period of time, the packing or O-rings become worn and need repair. In order to repair prior art spray guns, the guns have to be taken apart and the packing redone. When O-rings are used, the guns have to be completely disassembled with the interior portions removed and new O-rings provided to the sealing ports. This task was often time-consuming and difficult for a typical operator to undertake. Therefore, it is possible that a number of extra spray guns are needed in an operation so that the employees would always have an operating gun while others are being repaired.
If the operator did not realize that the seals were becoming worn, he could continue to apply the mixture to a work piece wherein the mixture was not of the proper proportions because of leaking of the seals. Also, the gun can be damaged by allowing pressure to accumulate in a portion of the gun.
When the leak is found and it is decided that the seal needs to be replaced, the gun has to be disassembled, and the remaining seal material cleaned out by digging into a component of the gun. This is both a time consuming and unpleasant task.
Other problems associated with these guns include, the air supply to the chopper portion of the gun often has to be turned on and off independently of the valving of the resin and catalyst. The trigger of the gun typically controls only the resin and catalyst whereas a separate air supply valve can be turned on for the chopper air supply. If the chopper air supply and the chopped fiberglass were not opened simultaneously with the flow of the resin/catalyst mixture, fiberglass fibers could be released into the environment where the work piece is being sprayed.
It is, therefore an object of the present invention to provide an improved spray gun.
It is a further object of the invention to provide a spray gun that is lightweight and easy for the operator to handle.
It is still another object of the invention to provide a spray gun with two independent piston mechanisms for the catalyst and the resin valving.
It is still a further object of the invention to provide a trigger mechanism that uses air to simultaneously open both the resin and catalyst pistons driven valves and also uses air to simultaneously close both the resin and catalyst positions driven valves.
It is yet a further object of the invention to provide a spray gun where leakage of the catalyst and/or resin can be detected readily by the operator.
It is still a further object of this invention to provide a spray gun in which the packing and/or O-ring seals can be easily adjusted from an exterior portion of the spray gun.
It is yet another object of the present invention to provide a spray gun with seals and O-rings easily replaceable without completely disassembling the gun.
It is still a further object of this invention to provide a spray gun having a cartridge type packing seal that is easily replaceable without the typical digging of the packing material out of the spray gun orifice.
It is still yet a further object of this invention to provide a valve means to operate the air supply to the chopper valve in conjunction with the operation the resin and catalyst valves.
These and other objects are attained in the provision of the spray gun apparatus for a fiberglass spraying system having a resin valve and a catalyst valve operated by separate pistons and actuated simultaneously by a trigger actuated air control valve. The use of the dual pistons cuts down the weight and the size of the spray gun and provides a more reliable spray gun. Air opens and closes the pistons, therefore, there is no need for springs and no sticking of handle valves. However, springs can still be used as a back-up system. The trigger mechanism is a four way air valve in that it opens two valves and also closes two valves.
The spray gun includes a leak detection to determine when the packings and O-ring seals of the resin and catalyst valve need to be adjusted, repaired or replaced. The packing is easily adjustable from exterior of the spray gun by rotation of the resin valve seat. The O-ring seals are easily removable from the spray gun by external separating the spool valve portion from the piston portion in order to be replaced quickly and efficiently. The packing is included in a cartridge type packing in order to quickly replace the entire packing seal. The catalyst valve controls the mixing of catalyst and a second air supply prior to spraying. Refinement air from the same air supply as used to actuate the resin and catalyst valves is controlled by a metering valve independent of the trigger actuated air control valve.
In a specially preferred embodiment of the subject invention, the catalyst piston further includes a portion which simultaneously opens an air valve to control the chopper air supply. This allows all of the raw materials to be controlled by pulling on a single trigger.
Other objects, advantages and novel features of the present invention will now become readily apparent upon consideration of the following descriptions of preferred embodiments in conjunction with the drawings.